1. Field of the Invention
The present invention relates to a fundus blood vessel examination apparatus used in equipment for measuring blood vessels of the fundus of an eye and blood flow or bloodstream information.
2. Related Background Art
Conventionally, a fundus hemodromometer or blood flow meter that can easily measure the absolute value of blood flow velocity on blood vessels of the fundus or eyeground of an eye using a Doppler shift is disclosed in Japanese Patent Application Laid-Open No. 9-154819. Such a fundus hemodromometer can reliably measure the blood flow velocity independently of the measurement portions of the blood vessels of the fundus. However, measurement is often disabled since a high-quality Doppler shift measurement signal cannot be obtained, depending on measurement positions even on a single blood vessel. This is because the blood vessels of the fundus are located deep inside a living body and indefinite factors of a living body have a large influence on such measurement.
However, in such case, by shifting the measurement position on a given blood vessel, a portion where a high-quality Doppler shift measurement signal can be obtained is detected. For this reason, a simple method of changing the measurement position on a blood vessel is required. As such method, a method in which an ophthalmic technician appropriately moves a fixation reference mark to change the direction of an eye to be examined of a patient, a method of deflecting a measurement light beam using a mirror, and the like, may be used.
However, in the above prior art, it is technically very difficult for the ophthalmic technician to change the measurement position by accurately tracking a blood vessel of the fundus that runs in a complicated pattern by his or her own sight and skills, and such technique is largely influenced by unstable fixation of an eve when a patient suffers a disease or is aged.
It is an object of the present invention to provide a fundus blood vessel examination apparatus, which can solve the aforementioned problems, and can move measurement light along the running direction of a blood vessel by automatically detecting the direction it runs.
It is another object of the present invention to provide a fundus blood vessel examination apparatus, which can accurately track measurement light on a blood vessel by a simple operation in combination with tracking of the diameter direction of the blood vessel.
It is still another object of the present invention to provide a fundus blood vessel examination apparatus, which evaluates the reliability of measurement data, and searches for a portion where optimal data can be obtained by automatically tracking measurement light on a blood vessel.
A fundus blood vessel examination apparatus according to the present invention comprises an irradiation optical system for irradiating a fundus blood vessel with measurement light, light-receiving means for receiving scattered light of the measurement light from the fundus blood vessel, measurement means for detecting predetermined information from the fundus blood vessel on the basis of information from the light-receiving means, direction detection means for detecting a direction in which a bloodstream flows in the fundus blood vessel, and control means for controlling the irradiation position on a fundus on the basis of the running direction information detected by the direction detection means, wherein the irradiation position moves along the direction in which the fundus blood vessel runs.
After the irradiation position of the measurement light is moved, the direction in which the fundus blood vessel runs is detected to determine a moving direction of the blood.
The measurement means comprises evaluation means for evaluating the reliability of the predetermined information, and the evaluation means evaluates the reliability of the predetermined information as needed after the irradiation position of the measurement light is moved.
The control means changes the irradiation position on the basis of an evaluation result of the evaluation means, and moves the measurement light to a nearby position where the predetermined information produces a predetermined reliability.
A fundus blood vessel measurement apparatus according to the present invention comprises:
presentation means for presenting a fixation reference mark to an eye to be examined;
irradiation means for irradiating a blood vessel on a fundus of an eye with measurement light in accordance with a position of the fixation reference mark;
light-receiving means for receiving reflected light of the measurement light by the fundus;
computation means for computing blood vessel information of a fundus blood vessel on the basis of a light-received output of the light-receiving means;
direction detection means for detecting a longitudinal direction of the blood vessel; and
position control means for controlling the position of the fixation reference mark in accordance with the direction detected by the direction detection means.
The apparatus further comprises an input member for changing the position of the fixation reference mark, and the position control means controls the position of the fixation reference mark on the basis of a direction detection signal from the direction detection means and an input signal of the input member.
The direction detection means comprises an image sensing element for sensing a blood vessel image.
The direction detection means further comprises an image rotator, which is inserted between the image sensing element and the eye to be examined, and is adapted to rotate the blood vessel image with respect to the image sensing element.
The image rotator is rotated in accordance with an output from the image sensing element.
The image rotator is rotated in accordance with an output from the image sensing element to locate the blood vessel image in a predetermined direction.
The direction detected by the direction detection means is a rotation angle of the image rotator.
The position control means controls the position of the fixation reference mark to irradiate the blood vessel with the measurement light along a longitudinal direction thereof.
The image sensing element comprises an array-type sensor.
Other features of the present invention will become apparent from the following description.